Theodore de Leo de Laguna (July 22, 1876 – September 22, 1930) was an American philosopher who taught for years at Bryn Mawr College and was known as an early feminist.

[1][2][3][4] His mother died young, and he was raised by his older sister Frederica.

Upon his return he taught at Cornell, where he met and, in 1905, married Grace Mead Andrus.

[2] In 1905, he accepted a position as a professor at the University of Michigan.

[2] In 1907 Theodore began teaching philosophy at Bryn Mawr College.